1. Field of the Invention
This invention relates generally to an apparatus for recording and/or reproducing information signals, such as, video signals, in successive parallel tracks on a magnetic tape or other record medium by means of transducers or heads which scan such tracks as the record medium is advanced, and is more particularly directed to an improved servo-control system for ensuring accurate scanning of the successive tracks by the heads of transducers during reproducing operation of the apparatus.
2. Description of the Prior Art
In existing apparatus, such as, a so-called VTR, for recording and/or reproducing video signals on a magnetic tape by means of rotary recording and/or reproducing heads which scan successive parallel tracks extending across the tape as the latter is longitudinally advanced, a predetermined interval of the video signals, such as, a field or frame interval, is applied to each rotary head during the scanning by the latter of a track extending across the tape so that such field or feame interval of the video signals will be recorded in the respective tracks. Further, during such recording operation of the apparatus, a control signal or pulse indicative of the rotational position of the rotary heads and/or the commencement of each field or frame interval of the video signals being recorded is applied to a fixed transducer or head for recording on a longitudinal edge portion of the tape as the latter is advanced past the fixed head. During reproducing operation of the apparatus, a fixed head reproduces the control signals recorded at spaced apart locations along the longitudinal edge portion of the tape as the latter is advanced past such fixed head, and such reproduced control signals are compared with pulse signals indicative of the rotational position of the rotary recording and/or reproducing heads in a servo-control system for regulating the advancement of the tape relative to the repeated traversing thereof by the rotary heads for ensuring that the latter will accurately scan the successive parallel tracks in which the video signals are recorded.
The foregoing servo-control system has been generally satisfactory so long as the tape is advanced at a substantial speed during recording and reproducing operations. However, it has recently been proposed to provide a video signal recording and/or reproducing apparatus, as aforesaid, in which the speed of advancement or transport of the tape is extremely low so as to substantially reduce the jitter components contained in the reproduced video signals. With such a very low speed of advancement of the tape, the fixed head is incapable of providing a sufficiently high level of reproduction of the control signals recorded along an edge portion of the tape and, accordingly, the existing servo-control system is unable to maintain accurate scanning or tracking of the successive parallel record tracks by the rotary heads during reproducing operation.